C# – How to Clone Object into Subclass Object

c++copyobjectsubclass

I have a class A and a class B that inherits class A and extends it with some more fields.

Having an object a of type A, how can I create an object b of type B that contains all data that object a contained?

I have tried a.MemberwiseClone() but that only gives me another type A object. And I cannot cast A into B since the inheritance relationship only allows the opposite cast.

What is the right way to do this?

Best Answer

There is no means of doing this automatically built into the language...

One option is to add a constructor to class B that takes a class A as an argument.

Then you could do:

B newB = new B(myA);

The constructor can just copy the relevant data across as needed, in that case.

Related Solutions

C# OOP – How to Copy an Instance of an Object

Then you need to implement ICloneable and replace

r.TryAddPackage((IPackage)ps);

with

r.TryAddPackage((IPackage)ps.Clone());

It's up to you to decide how Clone should populate the new instance of PinnacleStock that it returns.

At the most basic level, you could say

public PinnacleStock : ICloneable {
    public PinnacleStock Clone() {
        return (PinnacleStock)this.MemberwiseClone();
    }
    object ICloneable.Clone() {
        return Clone();
    }
    // details
}

This will just do a shallow copy of PinnacleStock. Only you know if this is the correct semantics for your domain.

C# – How to Clone an Inherited Object

Yes, MemberwiseClone will also copy the Checker-only fields. MemberwiseClone cannot know the return type of your Clone method; therefore, it's behaviour cannot depend on it.

About the difference betweeen your Clone implementation and the serialization: MemberwiseClone creates a shallow copy of the Tiles: If a Tile (or Checker) references some object, the Tile's clone still references the same object (rather than a copy of it).

On the other hand, your serialization code is a well known practice for creating a deep copy of your board: The whole tree of dependent objects is serialized and deserialized.

Of course, this only makes a difference if your Tiles (or Checkers) contain fields with reference types.

Best Answer

Related Solutions

C# OOP – How to Copy an Instance of an Object

C# – How to Clone an Inherited Object

Related Question